Effect of Long-Term Aging on Thermoelectric Properties of Tin Telluride Based Semiconductor Solid Solutions

Abstract

At present, with ever-increasing energy consumption, there is a significant interest in research and practical applications in the field of direct thermoelectric (TE) conversion of thermal energy into electrical one. An important property of TE generators and refrigerators from a practical point of view is their lifetime, which largely depends on the material used in a converter. The object of this study is solid solutions $(\text{SnTe})_{100-\mathrm{x}}(\text{In}_{2}\text{Te}_{3})_{\mathrm{x}}(\chi=0-8)$ based on tin telluride Sn'Te, into which In2 Te3 was introduced. After synthesizing polycrystals and measuring their properties (microhardness $H$, Seebeck coefflcient $S$, electrical conductivlty $\sigma$ and TE power factor $P=S^{2}\cdot\sigma)$, we kept them at room temperature in air without a special protective coating for 20 years. After measuring their properties after the long-term aging, we found that the general behavior of the $H(\chi), S(\chi), \sigma(\chi)$, and $P(\chi)$ dependences (specifically, an increase in $H, S, P$ and a decrease in $\sigma$ with increasing x) did not change. However, the long-term aging led to a more distinct manifestation of percolation effects accompanying the transition to heavy doping, as well as the processes associated with the formation of complexes in a solid solution. As a result, the composition dependences of mechanical and TE properties acquired an oscillatory character, but their monotonic component almost coincided with the dependences measured before the aging.